Method of making a printing plate

ABSTRACT

A method of making a printing plate having an image formed in relief thereon in which a copy of the image is placed over a layer of a light sensitive emulsion carried on a rigid backing plate. The copy and emulsion are exposed to light, with the image masking the underlying portion of the emulsion. The masked portion of the emulsion is removed and the remaining emulsion is cured into a rigid state with a recess disposed therein corresponding to the size and shape of the image. The cured emulsion is then placed in contact with an uncured pliable plateforming material, and said material is formed into a selfsupporting state with a reproduction of the image projecting therefrom.

United States Patent [191 Fishburn A METHOD OF MAKING A PRINTING PLATE[75] Inventor: Charles E. Fishhurn, Indianapolis,

Ind.

[73] Assignee: National Printing Plate Co., Inc.,

Indianapolis, Ind.

22 Filed: Mar. 22, 1973 [21] Appl. No.: 343,734

Related US. Application Data [63] Continuation-impart of Ser. No.208,857, Dec. 16,

1971, abandoned.

[111 3,806,575 [451 Apr. 23, 1974 OTHER PUBLICATIONS DuBois, J. H.Plastics, 1943, American Tech. Society, Chicago, P. 294 only.

Primary Examiner-David Klein Attorney, Agent, or Firm-Trask, Jenkins &l-lanley [5 7] ABSTRACT A method of making a-printing plate having animage formed in relief thereon in which a copy of the image is placedover a layer of a light sensitive emulsion carried on a rigid backingplate. The copy and emulsion are exposed to light, with the imagemasking the underlying portion of the emulsion. The masked portion ofthe emulsion is removed and the remaining emulsion is cured into a rigidstate with a recess disposed therein corresponding to the size and shapeof the image. The cured emulsion is then placed in contact with anuncured pliable plate-forming material, and said material is formed intoa self-supporting state with a reproduction of the image projectingtherefrom.

7 Claims, 6 Drawing Figures METHOD OF MAKING A PRINTING PLATE Thisapplication is a continuation-in-part application of my copendingapplication Ser. No. 208,857, filed Dec. 16, 1971 now abandoned.

BACKGROUND OF THE INVENTION plate. A thermoplastic mold material is thenbrought into contact with the etched plate to form the mold for thesubsequent formation of the printing plate itself. After this mold hasbeen formed, it is brought into contact with uncured plate-formingmaterial, and said plate-forming material is cured while it remains incontact with the mold to form the finished printing plate.

This process has certain inherent disadvantages. The etching step is aslow and laborious operation requiring the use of skilled craftsmen.Even with the use of such skilled craftsmen, mistakes and lackof properdefinition between the image to be produced and the image subsequentlyproduced on the plate arise. Further, if the etched zinc plates are tobe re-used for forming a different printing plate, they must be meltedand recast for the subsequent etching operation.

It is an object of this invention to overcome the difficulties anddisadvantages of the conventional printing platemanufacturing methodjust described. More particularly, it is an object of the instantinventionto eliminate the necessity for performing the etching step as vpracticed in such conventional methods.

SUMMARY OF THE INVENTION made thereof. The positive is placed on a layerof alight sensitive emulsion carried on a rigid backing plate with itsimage copy masking the underlying portion of the emulsion. The emulsionand positive are exposed to light, and after such exposure, the positiveis removed. The exposed emulsion is washed with water-to removetherefrom its masked portion and thereby form in the emulsion a recesscorresponding in its configuration to the image.

In order to give the recess in the emulsion layer the desired depth, asubsequent layer of emulsion without a backing plate applied thereto isdisposed over the first emulsion layer and bonded thereto. The positiveis then mounted on the second layer, and the steps of exposing thepositive and second emulsion layer to light and the subsequent removalof the masked portion of the second emulsion layer are repeated so thatthe first and second layers of the emulsion act in combination toprovide a laminate having a recess corresponding to the size andconfiguration of the'image and having a depth equal to the thickness ofthe two emulsion layers. This sequence of applying subsequentemulsionlayers and exposing and removing their masked portions is repeated untilan emulsion laminate having a recess of the desired depth is formed.

After the desired recess depth has been achieved, the emulsion laminateis cured into a rigid state and then placed in contact with an uncuredpliable plate-forming heat and pressure into the finishedself-supporting plate having the image formed in relief thereon, whichplate can then be stripped from the emulsion laminate.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings illustratethe invention. In such drawings:

FIG. 1 is a diagrammatic representation of a flow diagram showing theprocessing steps in carrying out the invention, with Steps 1 and 3 beingshown in exploded form and Step 5 being shown in section;

FIG. 2 is a perspective view of the printing plate made according to theprocessing sequence shown in FIG. 1;

FIG. 3 is a diagrammatic representation of a flow diagram showinganother embodiment of the invention, with Steps 1 and 3 being shown inexploded form and Step 5 being shown in section;

FIG. 4 is a perspective view of a printing plate formed I DETAILEDDESCRIPTION OF THE PREFERRED EMBODIMENT In carrying out my invention, Ifirst form a photographic positive 12 from the art work containing theimage to bereproduced on the printing plate 10. The positive 12, which"contains a photographic copy 13 of the image, is formed by conventionalphotographic techniques.

After the positive 12 has been formed, it is placed over and in contactwith a layer 14 of light sensitive emulsion fixedly bonded to a rigidbacking, conveniently a metal plate l6. The emulsion consists of aconventional emulsion base to which is added a light sensitive agentsuch as ammonium dichromate. The agent per se may be added directly tothe emulsion base or it may be combined with a carrier, preservative,and wetting agent such as in the Deep-Etch Positive Sensitizer sold byLith-Kem Corporation of Lynbrook, New York. The sensitizing agent, whenit is used alone, is added to emulsion base at the rate of about 1 ounce(avoirdupois) of sensitizer per fluid ounces of emulsion base, but whensaid Deep-Etch Positive Sensitizer is used, that material must be addedto the emulsion base at the rate of about one fluid ounce per eightfluid ounces of emulsion base to get the proper amount of the activesensitizing agent.

For reasons that will become more apparent hereinafter, the back plate16 'is a heat conductive metal plate. I have achieved excellent resultsusing aluminum for such a plate because of its heat conductiveproperties. The emulsion layer 14 is applied to the plate in a filmhaving a thickness of about .005 to about .050 inches.

After positive 12 has been placed in intimate contact with the emulsionlayer 14, they are exposed to light.

' The amount of such exposure will depend upon the intensity of thelight source, the thickness of the emulsion layer, and the spacingbetween the light source and the positive 12. During such exposure, theimage copy 13 on the positive 12 will, of course, mask the portion ofthe emulsion underlying it to shield said portion from the light whilethe lightpenetrates completely through the unmasked portions of theemulsion. After such exposure, the positive 12 is removed from theemulsion layer and the exposed emulsion is washed with water. The waterwashes away the previously masked portion of the emulsion and therebyforms a recess 18 in emulsion layer 14 corresponding to theconfiguration-of the image copy 13 on positive 12 as shown in Step 2 ofFIG. 1. Desirably, the water is at a temperature of about 100 F. If thetemperature is substantially lower, the washing step takes an excessiveamount of time. If the water temperature is substantially higher, caremust be exercised to prevent the emulsion from setting up into a rigidmass.

The light striking the emulsion causes it to partially cure. If agreater degree of cure is desired, the emulsion, after exposure, butbefore' .the water washing step,

=may have a developer sprayed thereon. One such developerwhich I haveemployed is sold under the name Deep-Etch Developer No. 3000 by theaforesaid Lith- Kem Corporation, and employs a mixture of hydroxyaceticacid, zinc chloride, calcium chloride, and potassium chloride as activeingredients.

'In most applications, the single emulsion layer 14 will not form arecess 18 of sufficient depth for producing the desired printing plateconfiguration. Therefore, as

shown in Step 3 of FIG. 1, a second emulsi'onlayer 20 is placed over thelayer 14. The emulsion layers are then heated to'a temperaturesufficient to bond them together, usually about 200 F. This forms anemulsion the previously formedrecess 18 in layer 16. This sequence ofapplying subsequent emulsion layers and exposing and washing them isrepeated until arecess haviing a desired depth is formed in the emulsionlayers.

As shown in Step 4 ofFlG. l, the recesses 18 and 18.

extend-downwardly through the emulsion layers'to the backing plate 16.l; have found that if any of the layers have a greater thickness thanabout .050 inches, the light, during the exposure step, cannot penetratefor the full depth of the emulsion layer. Further, the washing steptends to break away portions of the emulsion that were exposed to'light,thereby destroying the precise definition of the'image projection onthefinished plate. When emulsion layers having a thickness substantiallyless than'about'.00S inches are employed, it

will, of course, be necessary to use an'excessive number of emulsionlayers to form a laminate having the desired recess depth.

After the emulsion laminate has been formed containingan-image recess ofdesired depth, it is placed ov'erv a layer of uncuredpliable.plate-forming material 22 as shown in Step 5 of FIG. 1. A conventionalplateforming material 22 may consist of a moldablerubber latex. Thelaminate .is compressed against the plateforming material 22 at apressure of from about 400 to about 1,200 psi while the material 22 isheated to about 320" F. fot about minutes to cure into a selfsustaining'state. As shown in Step 5 of FIG. 1, the material 22 projects into therecesses 18 and '18 and is cured therein to thus form a projection 23 onthe finished plate 12 having aprinting face 27 corresponding in size andconfiguration to the image. After such curing, the finished plate l0canbe simply peeled from the emulsion layer laminate. I

If the emulsion laminate does nothave sufficient rigidity after itsexposure and before it is brought into contact with the plate-formingmaterial 22, the laminate may be cured. Such curing can be effected bysimply storing thelaminate until the emulsion has dried to ishedprinting plate. During such heat curing, the'backing plate 16, inaddition to giving rigidity to the emulsion laminate, will serve as aheat sink to effect an efficient and uniform curing of the emulsionlayers.

' As shown in FIG 4, it is frequently necessary to form I a printingplate 30 from art work or copy which has small images, such as forexample, fine printing. The projection 32on the plate 30 for such smallimages must havea sharp definition at its oute'ror printingface 33. Anembodiment of my invention which .is particularly well adapted to formsuch small image projections on a printing plate is shown in FIG. 3.

In carryingout the method sequence. shown in FIG. 3,the'art workcontaining the image is photographed twiceto produce twophotographicpositives 35 and 36. Informing the positive 35, the image copy 37 onthepositive slightly distorted to make said copy slightly larger than theimage on the art work being; photographed, while the positive 36 isformed with its image copy 38 the same size as the image on the artwork. Thus,'the' image copy-38 is smaller than the copy 37.

Afterthe positives 35 and 36 are -formed, positive,36

- is placed-on a light sensitive emulsion layer 40 mounted on backingplate 42, and said layer and positive are exposed to light with theimage copy 38. masking the underlying portion of the emulsion. When theexposure has beencompleted, the positive 35is removed, and the emulsionis washed to flush out its maskedportions and thereby form a recess 45in saidjemulsion which has the same size andconfiguration as the image.

I A second emulsion layer 47- is placed over the emulsion layer 40, andthey are heated to about 200. F. to

bond'tl'iem together and form an emulsion laminate. The positive 35 isplaced on the laminate. with its image copy 37 disposed in a centered oraligned position over removed, and the laminate is washed to flush outthe maskedportion of the emulsion layer and thereby forms'a recess45' insaid layer which is the same shape as, but larger than,-the image to'beproduced.

As'in the embodiment'previously described, if the laminate is notsufficiently rigid, it is'then cured into'a rigidstate in the mannerpreviously described. After curing, the laminate isplaced over alayer ofuncured pliable plate-forming material 50, and said material is curedinto a. rigid state while being compressed against the laminate in' thesame manneras previously described in connection'with Step 5 of FIG. 1to thus form the printing plate 30. f Y

As shown in FIGS. 4 and 5, because of the difference in the sizes of theimage copies 37 and 38, the image projection 32 on plate 30 will have atapered configuration. Thus, the base portion 52 of projection 32 willhave a greater cross-sectional extent than the printing face 33. Thiscreates a sharp definition of the image being printed and resists thetendency of the projection to bend as it is forced against the objectthat is being printed.

As with the embodiment shown in FIG. 1, any desired number of emulsionlayers may be employed to form the plate 30, the number of such layersdepending upon the depth of the recesses desired in the laminate. Whiletwo positives, such as positives 35 and 36, can be employed in producingthe recesses in a laminate containing more than two emulsion layers,additional positives can also be employed. in such case, it is desirableto have the image copies on such positives vary in size between thelargest such reproduction and the one corresponding to the exact size ofthe printing face 33 on the plate projection 32. in any event, the firstpositive to be exposed should be the one having an image reproductionsize corresponding to the desired size of the printing face 33. Whensuch successively sized image copies are employed with successiveemulsion layers, the projections 32 will have a gradual and smooth taperalong their length.

in the sequence shown in FIG. 3, it is to be understood that therecesses in the emulsion layers can be formed by the water wash alone orthe combination of the developer and water washing operations asdescribed in connection with the sequence shown in FIG.

As shown in FIG. 6, if the art work 60 upon which the image 62 if formedis made from a sheet 63 of transparent'or other non-opaque material,such as for example, acetate film, the art work itself can be employedwithout the necessity of forming a photographic positive. in such aprocess, the art work is laid directly on the emulsion with the image 62masking the underlying portion of the emulsion during the exposure step.After such exposure, the portion of the emulsion which was masked by theimage 62 is removed in the manner previously described to form a recessin the emulsion corresponding to the size and shape of the image. Ofcourse, in using the art work in this manner, a positive sensitizer isused-the same as with the positives 10, 35

1 and 36.

As will be understood, pairs of the art work sheets 60 having differentsized copies of the images can be employed in the same manner as thepositives 35 and 36 to produce tapered image projections on the finishedprinting plate like the projections 32 shown in FIGS. 4 and 5.

In the formation of any of the emulsion laminates wherein multiplelayers of emulsion are employed, as the layers 14 and 20, and the layers40 and 47, it is possible to eliminate the washing step in'between theexposures of the layers. Thus, the first emulsion layer can be exposed,the second layer bonded to the first layer, and exposed, and then asingle washing step is carried out to simultaneously form the recessesin both emulsion layers.

in the method described herein, it is to be understood that after theemulsion laminate has been used to form the finished plate or 30,,theemulsion layer or layers said plate can be used for formation ofsubsequent laminates.

I claim:

l. A method of making a printing plate having an image formed in reliefthereon, comprising the steps of forming a copy of a piece of workhaving said image thereon and placing said copy on a first layer of alight sensitive emulsion, exposing said copy and emulsion to light withthe image copy masking the underlying portion of said emulsion, removingthe masked portion of said emulsion, placing a second layer of saidemulsion on said first layer and bonding said layers together, placingsaid copy on said second layerof emulsion and exposing said copy andsecond layer of emulsion to light with the image copy masking theunderlying portion of said second layer, removing the masked portion ofsaid second layer, placing the emulsion layers in contact with a pliableplate-forming material, curing said material into a self-supportingstate while it is' maintained in contact with said emulsion layers, andseparating the cured plate-forming material from said emulsion layers.

2. A method of making a printing plate as set forth in claim 1 in whicheach of said emulsion layers has a thickness. of from about .005 toabout .050 inches, and said layersare bonded together by heating saidlayers to about 200 F.

3. A method of making a printing plate as set forth in claim 1 in whicheach of said emulsion layers has a thickness of from about .005 inchesto about .050 inches, and said. plate-forming material is cured byheating for about ten minutes at a temperature of about 320 F.

4. A method of making a printing plate as set forth in claim 1 in whichsaid masked portions of the emulsion are removed by washing said layerswith water.

5. A method of making a printing plate as set forth in claim 1 in whichsaid masked portions of the emulsion are removed by applying a developerto said emulsion layers and then washing them with water.

6. A method of making a printing plate having an image formed in reliefthereon, comprising the steps of making a first copy of a piece of workhaving an image thereon, making a second copy of said piece of workhaving the image thereon, the image on the first copy being larger thanthe image on the second copy, placing said second copy on a first layerof a light sensitive emulsion, exposing said second copy and emulsion tolight with the image on said second copy masking the underlying portionof the emulsion, removing the masked portion of said emulsion to form afirst recess in said emulsion corresponding to the image reproduction onsaid second copy, placing a second layer of said emulsion on said firstlayer and bonding said layers together, placing the first copy on saidsecond layer'with its image in alignment with said first recess andmasking the underlying portion of said second layer, exposing said firstcopy and second layer to light, removing the masked portion of saidsecond layer to form a second recess in said second layer correspondingto the image on said first copy and in alignment with said first recess,placing the emulsion layers in contact with a pliable plate-formingmaterial, curing said material into a selfsupporting state while it ismaintained in contact with said emulsion layers, and separating thecured plateforming material from said emulsion layers.

7. A method of making a printing plate having an image formed in reliefthereon, comprising the steps of forming a copy of a piece of workhaving said image thereon and placing said copy on a first layer of alight sensitive emulsion, exposing said copy and emulsion to light withthe image copy masking the underlying portion of said emulsion, placinga second layer of said emulsion on said first layer and bonding saidlayers together, placing said copy on said second layer of emulsion andexposing said copy and second layer of emulterial from said emulsionlayers.

2. A method of making a printing plate as set forth in claim 1 in whicheach of said emulsion layers has a thickness of from about .005 to about.050 inches, and said layers are bonded together by heating said layersto about 200* F.
 3. A method of making a printing plate as set forth inclaim 1 in which each of said emulsion layers has a thickness of fromabout .005 inches to about .050 inches, and said plate-forming materialis cured by heating for about ten minutes at a temperature of about 320*F.
 4. A method of making a printiNg plate as set forth in claim 1 inwhich said masked portions of the emulsion are removed by washing saidlayers with water.
 5. A method of making a printing plate as set forthin claim 1 in which said masked portions of the emulsion are removed byapplying a developer to said emulsion layers and then washing them withwater.
 6. A method of making a printing plate having an image formed inrelief thereon, comprising the steps of making a first copy of a pieceof work having an image thereon, making a second copy of said piece ofwork having the image thereon, the image on the first copy being largerthan the image on the second copy, placing said second copy on a firstlayer of a light sensitive emulsion, exposing said second copy andemulsion to light with the image on said second copy masking theunderlying portion of the emulsion, removing the masked portion of saidemulsion to form a first recess in said emulsion corresponding to theimage reproduction on said second copy, placing a second layer of saidemulsion on said first layer and bonding said layers together, placingthe first copy on said second layer with its image in alignment withsaid first recess and masking the underlying portion of said secondlayer, exposing said first copy and second layer to light, removing themasked portion of said second layer to form a second recess in saidsecond layer corresponding to the image on said first copy and inalignment with said first recess, placing the emulsion layers in contactwith a pliable plate-forming material, curing said material into aself-supporting state while it is maintained in contact with saidemulsion layers, and separating the cured plate-forming material fromsaid emulsion layers.
 7. A method of making a printing plate having animage formed in relief thereon, comprising the steps of forming a copyof a piece of work having said image thereon and placing said copy on afirst layer of a light sensitive emulsion, exposing said copy andemulsion to light with the image copy masking the underlying portion ofsaid emulsion, placing a second layer of said emulsion on said firstlayer and bonding said layers together, placing said copy on said secondlayer of emulsion and exposing said copy and second layer of emulsion tolight with the image copy masking the underlying portion of said secondlayer, removing the masked portions of said first and second layers,placing the emulsion layers in contact with a pliable plate-formingmaterial, curing said material into a self-supporting state while it ismaintained in contact with said emulsion layers, and separating thecured plate-forming material from said emulsion layers.